Table 1_Comprehensive analysis of the diatom genus Psammodictyon from Viet Nam: new species, molecular data, and fatty acid content.docx

IntroductionPsammodictyon is a widely distributed marine diatom genus with a complex taxonomy and underestimated species diversity.
MethodsLight and scanning electron microscopy, phylogenetic analysis and gas chromatography were used for study of the newly isolated strains of Psammodictyon.
ResultsTwelve strains of Psammodictyon were isolated from the coastal waters of central Viet Nam. Based on detailed morphological examinations using light and scanning electron microscopy, as well as molecular phylogenetic analysis, we propose six new species to science. Our phylogenetic analysis indicates that Psammodictyon forms a closely related monophyletic group. The resolution power of the short genetic markers (V4, V9 18S rRNA, V9-ITS1 18S rRNA, and a short region of rbcL), which are widely used for metabarcoding, is also discussed. Analysis of the fatty acid content of seven Psammodictyon strains showed that, like most diatoms, they accumulate high levels of polyunsaturated fatty acids (29.44–42.62%) and monounsaturated fatty acids (20.2–23.2%).
ConclusionThe number of known species in the genus Psammodictyon has increased to 21. Psammodictyon strains may be considered as potential producers of long-chain omega-3 polyunsaturated fatty acids.

引言：网脉藻属（Psammodictyon）是一个分布广泛的海洋硅藻属，其分类学关系复杂，物种多样性被显著低估。
材料与方法：本研究采用光学显微镜、扫描电子显微镜、系统发育分析及气相色谱法（Gas chromatography），对新分离得到的网脉藻属菌株开展研究。
结果：从越南中部近岸海域分离得到12株网脉藻属菌株。通过光学显微镜与扫描电子显微镜进行细致的形态学检视，并结合分子系统发育分析，我们向学界正式描述并发表6个新物种。本研究的系统发育分析结果显示，网脉藻属构成一个亲缘关系紧密的单系群。本研究同时探讨了当前元条形码测序（metabarcoding）领域广泛使用的短序列遗传标记（包括V4、V9区18S rRNA、V9-ITS1区18S rRNA以及rbcL的一段短序列）的分辨能力。对7株网脉藻属菌株的脂肪酸组成分析结果显示，与多数硅藻一样，该类群可积累高水平的多不饱和脂肪酸（占比29.44%~42.62%）与单不饱和脂肪酸（占比20.2%~23.2%）。
结论：目前网脉藻属已知物种数量已增至21种。网脉藻属菌株可被视为长链ω-3多不饱和脂肪酸的潜在生产菌株。